Pen



FIG. 1 is a front side perspective view of a pen showing my new design;

FIG. 2 is a side elevational view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a back elevational view thereof;

FIG. 5 is a bottom plan view thereof; and,

FIG. 6 is a top plan view thereof. 

The ornamental design for a pen, as shown and described. 